1. Field of the Invention
The present invention relates to an image processing apparatus, a control method therefor, and a storage medium storing a control program therefor. Particularly, the present invention relates to a sleep mode control for the image processing apparatus.
2. Description of the Related Art
Conventionally, a multifunctional peripheral device (referred to as an MFP below) that has a facsimile function, a printer function, a copy function, etc. is known as an image processing apparatus. There are some MFP's that are provided with a sleep mode for power saving. This sleep mode reduces power consumption rather than a standby mode. In the sleep mode, the power supply to a part of hardware may be cut off.
Generally, a shift condition needs to be satisfied when an MFP shifts to the sleep mode from the standby mode. For example, the shift condition is satisfied when a setting operation, an operational request from an external host connected via a LAN or USB, and an internal factor of the MFP, etc. do not occur during a predetermined time.
On the other hand, there are a plurality of return factors (release factors) for returning to the standby mode from the sleep mode. There is a mode control that changes the time for shifting to the sleep mode again from the standby mode according to the type of the return factor.
Here, when a release button is pushed in the sleep mode, an MFP releases the power saving and sets a transit time as a first time. Then, when the standby condition where a predetermined event does not occur continues over the first time after finishing the previous operation (a copy operation, for example), the MFP shifts to the sleep mode again. On the other hand, when an incoming call that is originated by a control apparatus is detected in the sleep mode in night, the MFP releases the sleep mode, and sets the transit time as s second time (second time<first time). When the standby condition where a predetermined event does not occur continues over the second time, the MFP shifts to the sleep mode again (see Japanese Laid-Open Patent Publication (Kokai) No. 2005-309016 (JP 2005-309016A)).
Incidentally, JP 2005-309016A does not take account of a case where a return factor is unknown when returning to the standby mode from the sleep mode. Here, an example where a call signal from a telephone line is used as a return factor in the facsimile function of the MFP will be described.
The call signal has a cadence (sequence) pattern of an ON signal and an OFF signal. In the sleep mode, the MFP returns to the standby mode from the sleep mode, when a call ON signal is detected. In this case, when a noise is mixed into the call signal under the effect of thunder etc. and a pulse-form call ON signal is inputted seemingly for example, the MFP cannot recognize an ON signal after returning to the standby mode. As a result, the MFP may fall into a state where the return factor from the sleep mode to the standby mode is unknown.
Then, even if the MFP returns to the standby mode from the sleep mode owing to an unknown return factor, when a new event does not occur over a definite time, the MFP shifts to the sleep mode from the standby mode again. However, the above-mentioned definite time is generally as long as tens of minutes from several minutes. Therefore, the total power consumption becomes large as compared with the case that re-shifts to the sleep mode immediately.
On the other hand, when the MFP is controlled so as to re-shift from the standby mode to the sleep mode in several seconds in order to reduce the total power consumption even if the return factor is unknown, the short re-shift time of several seconds may not allow a normal incoming operation by only repeating the return from the sleep mode and the re-shift to the sleep mode even when receiving a real call signal cadence pattern.